1. Field of the Invention
The field of the invention is that of power modulators and in particular modulators that modulate the power supply of a radio-frequency (RF) amplifier.
The invention is more precisely concerned with pulse width modulators (PWM) for modulating the power supply of an RF amplifier to apply amplitude modulation.
Another field of the invention is that of energy conversion, in which field a high switching frequency (&gt;10 MHz) is required.
The PWM of the invention is well suited to applications including radar, active antennas, sonar, high bit rate telecommunications and many others thanks to the very fast response time of the modulator of the invention.
2. Description of the Prior Art
The person skilled in the art knows of power converter modulators that are capable of operating at high switching frequencies.
These prior art modulators use the principle of resonance to obtain relatively high switching frequencies.
However, because they rely on resonance, these prior art switch mode modulators are subject to an upper frequency limit (&gt;1 MHz). Higher switching frequencies (5 MHz to 10 MHz) are advantageous for the power supplies of RF amplifiers in conditions which lend themselves to optimum energy efficiency.
Also because of resonance, the switching frequency of the transistors is dependent on the input voltage and on variations in the load. This restricts applications in telecommunications, which become problematical because the frequency spectrum of the various signals must be known. Variations in unwanted frequency components make it difficult to filter them out and the noise power varies with the switching frequency.
A second problem is that all existing implementations use power components and transfer techniques suited to low frequencies (a few tens of MHz), which limits the application for high bands.